There are a number of U.S. patents that disclose electronic apparatus for printing indicia on labels, some of these are restricted to hand held units and others that disclose tabletop units. Hand held labeling machines are disclosed, for example, in U.S. Pat. Nos. 4,264,396, Stewart; 4,407,692, Torbeck; 4,473,426, Goodwin et al.; 4,477,305, Hamisch; 4,490,206, Makely 4,497,683, Hamisch; 4,498,947, Hamisch et al.; 4,511,422, Hamisch et al.; 4,544,434, Mistyurik; 4,556,442, Torbeck; 4,561,048, Hamisch et al.; and 4,680,078, Vanderpool et al. Tabletop units for this general purpose, some of which are portable are described in U.S. Pat. Nos. 4,440,248, Teraoka; 4,501,224, Shibayama; 4,630,538, Cushing; and 4,655,129, Wirth et al.
The electronic machines for printing labels of the type disclosed above all include the same general combination of elements, a print head, means for feeding labeling media to be printed past the print head, a microprocessor, a read only memory programmed with appropriate instructions to operate the microprocessor, a random access memory, a keyboard with letter, number, and function keys for the entry of alphanumeric information and instructions concerning the indicia to be printed, and a visual display such as a LED, LCD unit to assist the operator in using the machine. In a hand held printer, these components may all be enclosed in a single housing.
A particular type of print head employs thermal transfer printing technology. Thermal transfer printing uses a heat generating print head to transfer a pigment, such as wax, carbon black, or the like, from a thermal transfer ribbon on to a labeling media. By using digital technology, characters are formed by energizing a sequence of pixels on the print head which in turn melt the wax or other pigment on the ribbon transferring the image to the labeling media.
The labeling media comprises a series of labels that are attached to a carrier strip. The carrier strip is fed through the printer and images are printed on the labels. The labels are then removed from the carrier and attached to the objects needing identification. As there are many types of label applications, there are many combinations of labels and carrier strips that provide labels of varying sizes, colors and formats.
Many of the label printers of the type described above are capable of printing on labels of varying sizes and with varying formats. Care must be taken by the user, therefore, to ensure that the labeling media loaded on the printer is compatible with the printing format desired. A mismatch between the format and labeling media may result in the printer printing unusable labels with the user having no means of determining whether the problem lies in the printing machine itself, or in the labeling media, or in the incompatibility of the two.
In addition, many label printers are designed for printing on labeling media that meets certain physical criteria. A user has no way of reliably knowing whether the labeling media that has been purchased is compatible with the particular printer and meets the printer manufacturer's standards. A mismatch between the labeling media and the printing machine may cause damage to the printing machine, again with no means to determine the cause of the damage.
Generally, the label type is manually entered by the user through the printer keyboard. This provides the printer with the information required to properly print labels in the correct format. This method is subject to user error and it does not address the problem of using print media that is physically incompatible with the printer.
Methods are known in the art that address the problem of using incompatible labeling media. One approach is to provide an adjustable platen for a label printer which accommodates media of widely different widths and thicknesses as is disclosed in U.S. Pat. No. 5,372,443, Borucki et al. While this approach reduces the compatibility problem by enabling the printer to work with a wider range of print media types, the compatibility problem still exists. In addition, such mechanical measures are of no assistance in differentiating print media designed for use in thermal printers.
Another solution to the compatibility problem that is used in large printers is to provide an electronic means for the printer to identify the particular print media being used. In U.S. Pat. No. 5,318,370, Nehowig, for example, the print media is contained in a cassette and a memory chip mounted in the cassette stores information about the print media. When the cassette is inserted in the printer, this information is read by the printer and used to control its operation. This approach has not been applied to hand held printers where the print media is supplied in a roll that is supported on a removable spool.